Abstract: In order to quickly screen the content of fipronil and its metabolites in the aquaculture water, a method for the detection of fipronil and its metabolites in the aquaculture water was established by using the liquid-liquid extraction pretreatment and the high-performance liquid chromatography-tandem mass spectrometry. The optimized pretreatment conditions were as follows:100.0 mL aquaculture water was selected after the filtration, and the petroleum ether was used as the extraction solvent. After shaking well, the supernatant was taken and extracted for 3 times. The extracting solution was dried by nitrogen below 40℃, redissolved with 1.0 mL methanol water, passed through the membrane, and detected on the machine. The chromatographic conditions were as follows:the chromatographic column was Eclipse Plus C18, the mobile phase was methanol-water, and the fipronil and its metabolites were well separated within 7 min. The mass spectrometry conditions were as follows:the electrospray ionization source (ESI); simultaneously scanning by using the negative ion mode; the acquisition mode with the multiple reaction monitoring (MRM). Fipronil and its metabolites had a good linear relationship in the range of 10 ng·mL^-1-500 ng·mL^-1, the correlation coefficient was not less than 0.999, the average recovery rate was 65.9%-88.5%, and the relative standard deviation was 1.8%-13%. The signal-to-noise ratio (SNR) was all greater than 10 when the limit of quantification of each component method was 0.1 ng·mL^-1. The method was suitable for the rapid detection of fipronil and its metabolites in the aquaculture water.